1. Field of the Invention
The present invention relates to a method and apparatus for quantitatively evaluating scintillation caused by surface unevenness. The present invention also relates to an antiglare film and a method of producing the same.
2. Description of Related Art
In display units such as LCDs, a phenomenon known as xe2x80x9cscintillationxe2x80x9d may occur. This is one of causes that make it difficult for the viewer to see the display. Scintillation is a phenomenon in which when the screen of a display unit is lit up, fine unevenness of luminance appears on the screen, and the position of the luminance unevenness appears to change as the viewing angle is changed. Scintillation is likely to appear particularly when white or green is displayed over the whole screen. Display units need to undergo an evaluation of the degree of such scintillation. The conventional practice is to use a 20-degree specular glossiness measuring method in which the intensity of light regularly reflected from a specimen when light is incident thereon at an angle of 20 degrees is measured. However, scintillation occurs due to surface unevenness or the like. Therefore, scintillation cannot accurately be evaluated by a method in which the intensity of reflected light is measured. Accordingly, a visual evaluation method has heretofore been employed to judge the quality of an antiglare film used to prevent scintillation.
However, it cannot be denied that the visual evaluation of scintillation is likely to cause differences between individuals in the evaluation and lacks accuracy. In development of antiglare films, etc., it has been demanded that the intensity of scintillation should be made capable of being evaluated quantitatively in order to understand the performance of antiglare films, etc.
To solve the above-described problem, an object of the present invention is to provide a method capable of quantitatively evaluating the intensity of scintillation, which changes with surface unevenness or the like.
Another object of the present invention is to provide an antiglare film superior in scintillation preventing characteristics.
The present invention provides a method of quantitatively evaluating scintillation. According to the evaluation method, light from a white light source is made incident on a surface of an object to be measured through a matrix filter. Reflected light or transmitted light from the object is photographed and captured as data. Image processing is performed for the luminance distribution of the captured light to obtain a standard deviation of the dispersion of the luminance distribution. The value of the obtained standard deviation is defined as a scintillation value of the surface of the object.
The object may be an antiglare film.
The performance of the object may be evaluated by judging whether or not the scintillation value is greater than a predetermined value.
Preferably, the predetermined value for the scintillation value is 15 when the scintillation value is measured at a mean luminance of 145 cd/m2 of the captured image.
In addition, the present invention provides an apparatus for quantitatively evaluating scintillation. The apparatus includes at least a white light source, a matrix filter, a photographing device, and a computer. Light from the white light source is made incident on a surface of an object to be measured through the matrix filter. Reflected light or transmitted light from the object is photographed with the photographing device and captured as data. The data is processed by the computer to obtain a standard deviation of the dispersion of the luminance distribution. The value of the standard deviation thus obtained is defined as a scintillation value of the surface of the object.
In the above-described evaluation apparatus, the photographing device may be a CCD camera.
The object may be an antiglare film.
The performance of the object may be evaluated by judging whether or not the scintillation value is greater than a predetermined value.
Preferably, the predetermined value for the scintillation value is 15 when the scintillation value is measured at a mean luminance of 145 cd/m2 of the captured image.
In addition, the present invention provides an antiglare film whose scintillation value is greater than zero and not greater than 15 when measured at a mean luminance of 145 cd/m2 of a captured image.
In addition, the present invention provides a method of producing an antiglare film having an antiglare layer formed on at least one surface of a base. According to the production method, light from a white light source is made incident on a surface of the antiglare film through a matrix filter. Reflected light or transmitted light from the antiglare film is photographed with a photographing device and captured as data. Image processing is performed for the luminance distribution of the captured light by a computer to obtain a standard deviation of the dispersion of the luminance distribution. The standard deviation thus obtained is defined as a scintillation value of the surface of the antiglare film. The antiglare layer is formed so that the scintillation value is not greater than a predetermined value.
In the above-described production method, the photographing device may be a CCD camera.
Preferably, the predetermined value for the scintillation value is 15 when the scintillation value is measured at a mean luminance of 145 cd/m2 of the captured image.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.